Discharge lamp and lamp device

ABSTRACT

The present invention relates to a lamp device using a high-pressure vapor discharge lamp, particularly to an improvement for controlling the influence of the generation of heat, which accompanies an increase in lamp power and a reduction in the size of a reflector. A lamp device of the present invention comprises a discharge lamp having an arc tube enclosing luminescent materials and having a pair of opposing electrodes disposed therein and a pair of sealed portions extending from the arc tube; a reflector which reflects light radiated by the discharge lamp; a transparent member covering an open end of the reflector and accommodating the discharge lamp in a space between the transparent member and the reflector; and means for preventing an excessive temperature rise wherein the temperature rise of welded parts of wiring members electrically connected to the electrodes of the discharge lamp is restricted.

TECHNICAL FIELD

[0001] The present invention relates to a discharge lamp having a pairof opposing discharge electrodes and enclosing mercury, rare gases, andso forth in an arc tube. It also relates to a lamp device constructedsuch that this kind of discharge lamp is built into the inside of areflector. This lamp device can be used as, for example, the lightsource of a screen projector.

BACKGROUND ART

[0002] Conventionally, as, for example, the light source of a screenprojector, a lamp device provided with a discharge lamp, such as ahigh-pressure mercury vapor discharge lamp, inside a concave reflectorhas been used. A discharge lamp is constructed such that a pair ofopposing discharge electrodes is provided, and mercury, rare gases, andso forth are enclosed in an arc tube. In order that the interior of thearc tube be gastight, power is supplied to the discharge electrodes bymeans of wiring members enclosed in sealed portions, which are providedon both sides of the arc tube, and connected by welding or the like. Inaddition, by adjusting the discharge electrodes so as to be at acomparatively short distance from each other and forming an arc having ashort arc length (short arc), projected light is efficiently supplied toa specified optical system, and thus a bright image can be projected ona screen.

[0003] A discharge lamp such as the one described above is characterizedin that the arc tube reaches a very high temperature during operation.Specifically, in, for example, a 100 W to 150 W common short archigh-pressure mercury vapor discharge lamp, the maximum temperature ofthe arc tube (the interior wall surface side of the upper portion of thearc tube) is approximately 900° C. to 1000° C. In addition, thetemperature of the sealed portions is about 500° C., lower than theabove-mentioned maximum temperature, but still a rather hightemperature. For this reason, the wiring members disposed in the sealedportions are composed of a high melting point metal such as molybdenum.However, when the temperature of these sealed portions rises too much,the welded portions of the wiring members in the sealed portions andnear the sealed portions begin to oxidize, corrode, and the likeresulting in disconnection, and there is a risk of the lamp beingextinguished. Thus, in a common projector, a cooling fan is provided inthe main body of the projector making it possible to prevent anexcessive temperature rise of the discharge lamp and the reflector. Itis to be noted that, in order to prevent disconnection by oxidation andthe like of the welded portions of the wiring members as describedabove, it is thought that the temperature of the above-mentioned weldedportions should be regulated according to, for example, the standard(350° C.) specified in the regulations for halogen lamps, “TungstenHalogen Lamps,” IEC (International Electrochemical Commission) 60357 and“Halogen Lamps,” JIS (Japanese Industrial Standards) C7527, and it ispreferable to restrict the temperature to, at the highest, 400° C. orless.

[0004] In addition, the discharge lamp is characterized in that theinside of the arc tube reaches a very high pressure during operation.Specifically, in, for example, a 100 W to 150 W common discharge lamp asabove, the pressure (operating pressure) of the inside of the arc tubeapproaches 200 atmospheres. For this reason, when the arc tube isdamaged during lamp operation, large explosive sounds and the scatteringof glass fragments tend to result. The occurrence of these kinds oflarge explosive sounds and scattering of glass fragments, for example,especially when the discharge lamp is applied to projectors forhousehold use, is a factor in lowering the commercial value of the lamp.Thus, lamp devices which block the open end of the reflector with aglass plate to lower the frequency of explosive sounds and thescattering of glass fragments are widely used. When a completelyhermetically sealed space is formed between the reflector and the glassplate by the reflector and the glass plate, the temperature rise of thedischarge lamp is considerable. On the other hand, when a notch or thelike is provided in the reflector and/or the glass plate and outside airis circulated inside the lamp in order to cool the discharge lamp, inevent that the arc tube is damaged, substantial reduction in explosivesounds and consistent prevention of the scattering of glass fragmentsand dispersal of mercury vapor are difficult to achieve.

[0005] Furthermore, in recent years, there have been increasing demandsfor an increase in the brightness of projected images and a reduction inthe size of projectors. However, because increase in lamp power andreduction in the size of the reflector, which accompany these demands,invite an even greater temperature rise in discharge lamps, it has beendifficult to satisfy the demands. Therefore, in order to sufficientlysatisfy the increasing demands for an increase in the brightness ofprojected images and a reduction in the size of projectors, effectiverestriction of the temperature rise of a lamp device accompanying anincrease in output and reduction in the size of a reflector and aboveall restriction of a temperature rise at the welded portions of wiringmembers are needed.

DISCLOSURE OF THE INVENTION

[0006] In view of the foregoing problems, it is an object of the presentinvention to provide a high-pressure vapor discharge lamp and a lampdevice which, even with an increase in lamp power and a reduction in thesize of the reflector, can prevent disconnection due to oxidation andthe like of the welded portions of wiring members and the like and withwhich a lengthening of lamp life and a decline in the percentage ofdefective lamps can be expected. It is another object of the presentinvention to provide a lamp device that can reduce explosive sounds fromthe arc tube and consistently prevent the scattering of glass fragmentsand the dispersal of mercury vapor.

[0007] The foregoing problems are solved in one aspect of the invention,by the provision of a lamp device comprising:

[0008] a discharge lamp comprising an arc tube, the arc tube enclosingluminescent materials and having disposed therein a pair of opposingelectrodes, and a pair of sealed portions extending from the arc tube(namely, the sealed portions are coupled to the arc tube);

[0009] a reflector which reflects light radiated by the discharge lamp;

[0010] a transparent member covering an open end of the reflector andaccommodating the discharge lamp in a space between the transparentmember and the reflector; and

[0011] means for preventing an excessive temperature rise wherein thetemperature rise of welded parts of wiring members electricallyconnected to the electrodes is restricted.

[0012] In other words, according to the present invention, in a lampdevice accommodating a discharge lamp in a space formed by a reflectorand a transparent member covering the reflector, a means for preventingan excessive temperature rise of the wiring members and welded parts ofthe wiring members caused by the generation of heat accompanyingoperation of the lamp is provided. Through this means, it is possible tolimit thermal degradation of the welded parts of wiring members. Thus,disconnection at the welded parts is prevented, and a lengthening oflamp life and a decline in the percentage of defective lamps can beanticipated. In addition, demands for increased lamp power and reductionin the size of reflectors can be responded to without difficulty.

[0013] The discharge lamp may have a foil sealed construction.

[0014] The present invention is useful in so-called foil sealedconstruction discharge lamps, which are widely used. In foil sealedconstruction discharge lamps, metal foils, serving as the wiring membersin the sealed portions and capable of securing a large area of contact,are used such that adhesion is maintained despite the difference in thecoefficients of thermal expansion of the glass and the metal foils, andthe hermetic seal of the space in which the electrodes and so forth aredisposed is maintained despite damage from thermal shock between theglass that forms the sealed portions and the metal foils. One end of ametal foil, located in the end portion of a sealed portion, is connectedby welding to a conducting member that is connected to an external powersource. By providing a means for preventing an excessive temperaturerise, it is possible to prevent an excessive temperature rise at thewelded parts of the metal foils and the wiring members within the sealedportions, which reach high temperatures. In addition, the temperaturerise at the welded parts of wiring members which are outside the sealedportions but located near the sealed portions can be restricted.

[0015] Of course, even in lamp devices that use discharge lamps nothaving a foil sealed construction, for example, a discharge lamp havingrod-shaped wiring members sealed in the sealed portions or a dischargelamp in which the electrodes pass through the sealed portions,disconnection at the welded parts of the rod-shaped wiring members orthe electrodes and other wiring members can be prevented.

[0016] An inside space of the reflector and the transparent member maybe hermetically sealed in a gastight manner. Thus, in event that the arctube is damaged, explosive sounds can be greatly reduced and preventionof the scattering of glass fragments and the dispersal of mercury vaporcan be ensured.

[0017] The pair of sealed portions may have differing lengths and themeans for preventing an excessive temperature rise may be such that thelonger sealed portion is on the side of the transparent member and theshorter sealed portion is on the side of the base of the reflector.

[0018] More specifically, it is preferable that an end of the sealedportion on the side of the transparent member be positioned near thetransparent member.

[0019] In a lamp device, because the sealed portion on the side of thetransparent member reaches a higher temperature than the sealed portionon the side of the base of the reflector, the welded parts of the wiringmembers in the sealed portion on the side of the transparent member aremore subject to degradation by heat than are the welded parts of wiringmembers in the other sealed portion. In addition, in a discharge lamphaving a foil sealed construction, the welded part of the metal foil andthe conductive member on the side connected with an external powersource is more subject to degradation by heat than is the welded part ofthe metal foil and the discharge electrode, which reaches a highertemperature, due to the weakness of the gastight seal. Thus, asdescribed above, by adjusting the length of the sealed portions, becausethe distance from the front end of the sealed portion on the side of thetransparent member to the light-emitting portion is longer than that ofthe other sealed portion, the temperature of the front end of the sealedportion on the side of the transparent member can be restricted to a lowtemperature, and disconnection by oxidation and the like of the welds ofwiring members and the like in the front end of the sealed portion onthe side of the transparent member or near this front end can beprevented.

[0020] The means for preventing an excessive temperature rise may bemeans for channeling heat such that heat from the sealed portiondisposed on the side of the transparent member is conducted to theexterior of the lamp device.

[0021] For the means for channeling heat, it is possible to use, forexample, a copper plate or a heat pipe having one end wrapped around thesealed portion and the other end extended to the exterior of the lampdevice. By means of a heat channeling means such as this, because theheat of the sealed portion is released outside the lamp device, it isindeed possible to restrict the temperature of the front end of thesealed portion to a low temperature and to prevent disconnection byoxidation and the like of the welds of wiring members and the like.

[0022] The means for preventing an excessive temperature rise may besuch that the sealed portion disposed on the side of the transparentmember is integral with the transparent member

[0023] Thus, because heat from the front end of the sealed portion isreleased from the exterior surface of the transparent, hermeticallysealed member and the like, the temperature of the front end of thesealed portion can indeed be restricted to a low temperature, anddisconnection due to oxidation and the like of the welds of wiringmembers and the like can be prevented.

[0024] The means for preventing an excessive temperature rise may besuch that the front end of the sealed portion disposed on the side ofthe transparent member projects into the exterior of the transparentmember.

[0025] Thus, because the front end of the sealed portion is cooled byair from the outside, the temperature of the front end of the sealedportion can be restricted to a low temperature, and disconnection, dueto oxidation and the like of the welds of wiring members and the likecan be prevented.

[0026] A lamp device may further comprise cooling means for removingconducted heat to the exterior of the lamp device or for absorbingconducted heat.

[0027] For the cooling means, it is possible to use, for example, acooling fan, heat releasing fins, a cooling module utilizing a Peltierelement, or the like. Thus, because heat conducted by a heat channelingmeans, heat conducted to the surface or periphery of the transparent,hermetically sealed member, and heat from the front end of theprotruding sealed portion can be efficiently released, it is possible torestrict the temperature of the front end of the sealed portion to a lowtemperature without difficulty.

[0028] A high-pressure vapor discharge lamp may comprise:

[0029] an arc tube enclosing luminescent materials and having disposedtherein a pair of opposing electrodes; and

[0030] a pair of sealed portions extending from the arc tube, the pairof sealed portions having differing lengths.

[0031] By using a high-pressure vapor discharge lamp such as this one,it is possible to construct a lamp device which restricts thetemperature of the front end of a sealed portion to a low temperatureand thus can prevent disconnection due to oxidation and the like ofwelds of wiring members and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a longitudinal sectional view of a lamp device ofExample 1.

[0033]FIG. 2 is a longitudinal sectional view of a discharge lamp usedin the above-mentioned lamp device.

[0034]FIG. 3 is a longitudinal sectional view of a lamp device ofExample 2.

[0035]FIG. 4 is a longitudinal sectional view of an essential part ofthe above-mentioned lamp device.

[0036]FIG. 5 is a front view of the above-mentioned lamp device having acut out section.

[0037]FIG. 6 is a front view of another lamp device of Example 2.

[0038]FIG. 7 is a longitudinal sectional view of a lamp device ofExample 3.

[0039]FIG. 8 is a longitudinal sectional view of another lamp device ofExample 2.

[0040]FIG. 9 is a longitudinal sectional view of yet another lamp deviceof Example 3.

[0041]FIG. 10 is a longitudinal sectional view of a lamp device ofExample 4.

Reference Numbers

[0042]10 lamp device

[0043]11 reflector

[0044]11 a reflector surface

[0045]11 b lamp securing hole

[0046]11 c lead wire hole

[0047]12 glass plate

[0048]12 a hole

[0049]12 glass plate

[0050]22 arc tube

[0051]23 sealed portion

[0052]24 sealed portion

[0053]25 discharge electrodes

[0054]26 mercury

[0055]27, 28 metal foils

[0056]29, 30 metal rods

[0057]29 a, 30 a welds

[0058]31 lead wire

[0059]31 a welds

[0060]32 cap

[0061]33, 34, 42 cement

[0062]41 heat releasing device

[0063]41 a heat absorbing part

[0064]41 b heat channeling part

[0065]41 c heat releasing part

[0066]43 cooling device

[0067]51 cooling fan

[0068]52 filler

BEST MODE FOR CARRYING OUT THE INVENTION

[0069] In the following, as the preferred examples of the presentinvention, examples of lamp devices utilizing high-pressure mercuryvapor discharge lamps are explained in detail with reference to thefigures.

EXAMPLE 1

[0070] A high-pressure mercury vapor discharge lamp in which sealedportions are formed so that the lengths of the sealed portions areasymmetric and a lamp device utilizing the above-mentioned dischargelamp are explained.

[0071] A lamp device 10, as shown in FIG. 1, has, for example, anellipsoidal reflector surface 11 a and a reflector 11 with an open endhaving a diameter of 80 mm. In the inside of the reflector 11, forexample, a discharge lamp 21 having a lamp power (rated power) of 200 Wis disposed. The open end of the reflector 11 is hermetically sealed bya glass plate 12 such that, even when the discharge lamp 21 is damaged,prevention of large explosive sounds, the scattering of glass fragments,the dispersal of mercury vapor, and so forth is ensured.

[0072] The discharge lamp 21 has a pair of sealed portions 23 and 24coupled to both ends of an arc tube 22 respectively. The sealed portions23 and 24 are of different lengths, and the sealed portion 23 on theside of glass plate 12 is longer than the other sealed portion, thesealed portion 24. In addition, the sealed portion 23 is adjusted sothat the front end of the sealed portion 23 is positioned near the glassplate 12. In the inside of the arc tube 22, a pair of coiled orrod-shaped discharge electrodes 25 comprising tungsten, for example, isprovided and luminescent materials such as mercury 26, rare gases, andso forth (not shown in the figure) are enclosed. It is to be noted thatthe discharge lamp 21 is not limited to a high-pressure mercury vapordischarge lamp such as the one described above; a lamp such as one thatfurther encloses a halogen gas, a metal halide, or the like for the fillmaterial or one that does not contain mercury are also possibilities.

[0073] The sealed portions 23 and 24 comprise metal foils 27 and 28,comprising a high melting point metal such as molybdenum, electricallyconnected to the electrodes 25 respectively and glass tubes extendingfrom the arc tube 22. By the foil sealing of the metal foils 27 and 28and the glass tubes, a gastight discharge space in the arc tube 22 ismaintained. The pair of discharge electrodes 25 are welded to one of theends of the metal foils 27 and 28, comprising molybdenum, for example,respectively, which were sealed in the sealed portions 23 and 24. Theother ends of the metal foils 27 and 28 are welded, as shown in FIG. 2,to metal rods 29 and 30, comprising molybdenum and having ends exposedoutside of the sealed portions 23 and 24, by welds 29 a and 30 a. Themetal rod 29 is welded to a lead wire 31 by a weld 31 a. The metal rod30 is welded to a cap 32 covering an end of the sealed portion 24. Thedischarge electrodes 25 and the metal rods 29 and 30 are connected bymeans of the metal foils 27 and 28 sealed in the sealed portions 23 and24 as described above, so that the hermetic seal of the interior of thearc tube 22 is strengthened, and high pressure is maintained. That is,because of the difference in the coefficient of thermal expansion andthe like of the metal rods 29 and 30 and the glass, it is notnecessarily easy to improve adhesion between the metal rods and thesealed portions 23 and 24. By contrast, because the metal foils 27 and28 are very thin and the area of contact with the sealed portions 23 and24 is very large, it is possible to easily improve adhesion between themetal foils and the sealed portions, and therefore, the interior of thearc tube 22 can be easily maintained at a high pressure.

[0074] The discharge lamp 21 is disposed such that the gap between thepair of discharge electrodes 25 (discharge arc) is positioned at thefirst focal point of the ellipsoid of the reflector 11, and at the cap32 section, the lamp is sealed and secured into a lamp securing hole 11b, formed at the base of the reflector 11, with a cement 33. Inaddition, a lead wire 31 of the discharge lamp 21 passes through to theexterior of the reflector 11 through a lead wire hole 11 c formed on thewall surface of the reflector 11. The above-mentioned lead wire hole 11c is also sealed with a cement 34.

[0075] By forming the sealed portions such that the sealed portion 23 onthe side of the glass plate 12 is longer than the sealed portion 24 onthe side of the cap 32 as was described above, because the distancebetween the weld 29 a of the metal foil 27 and the metal rod 29 and thelight-emitting portion of the discharge lamp 21 is lengthened, it ispossible to restrict the temperature rise of the above-mentioned weld 29a. In the actual measurement of temperatures, a discharge lamp 21 havinga sealed portion 23 and a sealed portion 24 both with lengths of 25 mmwas operated at a lamp power of 200 W, and when the maximum temperatureof the arc tube 22 (the interior wall surface side of the upper portionof the arc tube) approached 1000° C., the temperature of the weld 29 arose to 507° C. In contrast, with a discharge lamp 21 in which thelength of the sealed portion 23 was made to be 35 mm and the length ofthe sealed portion 24 was made to be 25 mm, the temperature of the weld29 a was, at the highest, 388° C. This temperature is higher than theregulation temperature (350° C.) for halogen lamps as specified in IEC60357, but it is a sufficiently low temperature for the prevention ofoxidization, corrosion, and the like of the metal foil 27, the metal rod29, and the weld 29 a of the foil and rod. For this reason, even ifadhesion between the metal rod 29 and the sealed portion 23 diminishesand the above-mentioned weld 29 a and the like contact air in the lampdevice 10, it is possible to prevent disconnection due to oxidation,corrosion, and the like. At the same time, it is possible to restrictthe temperature rise of the welded part 31 a of the metal rod 29 and thelead wire 31 and also to prevent disconnection at the welded part 31 a.Accordingly, not only a lamp device utilizing a discharge lamp having afoil sealed construction as shown in FIG. 1, but also lamps utilizingdischarge lamps which have a single rod wiring member in place of themetal foil 27 and the metal rod 29 or lamps that pass one of theelectrodes 25 directly through the sealed portion 23 without using ametal foil 27 and expose the end of the electrode 25 to the outside ofthe sealed portion 23 can prevent disconnection at the welded part ofthe single rod wiring member or the electrode 25 and the lead wire 31.

[0076] When an ellipsoid mirror is used for the reflector 11 and alight-emitting portion is provided near the first focal point asdescribed above, it is conceivable that because light reflected off ofthe reflector 11 converges at the second focal point, the closer thefront end of the sealed portion 23 comes to the second focal point, thegreater the heating action of the reflected light. However, normally,because the action of temperature decrease by distancing the front endof sealed portion 23 from the light-emitting portion is greater than theheating action, it is possible to restrict the temperature of the frontend of the sealed portion 23 to a low temperature as described above. Itis to be noted that it is also possible to restrict the temperature ofthe front end of the sealed portion 23 to a lower temperature by forminga reflecting layer along the whole length of the sealed portion 23 or ona periphery of the sealed portion 23, such as the periphery near thefront end of the sealed portion 23 or the weld 29 a, thus reducing theheating action of the above-mentioned reflected light. In addition, incases in which the restriction of the temperature of the front end ofthe sealed portion 23 to a low temperature is obtained only by reducingthe heating action of the reflected light, such as when the lamp powerof the discharge lamp 21 is low, it is not always necessary to make thesealed portion 23 longer than the sealed portion 24.

EXAMPLE 2

[0077] An example of a lamp device provided with a means for releasingheat near a sealed portion of a discharge lamp to the exterior of thereflector is explained. It is to be noted that in the following aspectof the invention, the same reference numbers are used for elements ofthe construction having the same functions as those of the lamp deviceof Example 1, and explanation is omitted.

[0078] In this lamp device 10, as shown in FIGS. 3 to 5, a heatreleasing device 41, which releases heat near a sealed portion 23 of adischarge lamp 21 to the exterior of a reflector 11, is provided. Thisheat releasing device 41 comprises a material having a high thermalconductivity, such as copper plate, and is composed of a heat absorbingpart 41 a, which is wrapped around almost the whole length of the sealedportion 23, a heat channeling part 41 b, which channels heat from theheat absorbing part 41 a to the exterior of the reflector 11, and a heatreleasing part 41 c, which releases the channeled heat.

[0079] With the heat absorbing part 41 a constructed such that a copperplate or the like is only wrapped around the periphery of the sealedportion 23, the specified advantageous effects can be obtained, but inorder to obtain greater advantageous effects, the heat absorbing part 41a and the sealed portion 23 are adhered together. After interposing, forexample, glass powder, having a lower melting point than the sealedportion 23, and wrapping the copper plate, the structure is heated andadhered. In addition, although the larger the adhered area (adheredlength) of the heat absorbing part 41 a with the sealed portion 23, thegreater the advantageous effects of heat absorption, it is possible, notonly to have a structure in which the heat absorbing part 41 a iswrapped around the whole length of the sealed portion 23, but to have astructure in which the heat absorbing part 41 a is wrapped aroundsections of the sealed portion 23 insofar as the temperature rise nearthe weld 29 a can be restricted.

[0080] The heat channeling part 41 b is set up with the surface of thecopper plate perpendicular to the glass plate 12 such that the projectedarea in the direction of the optical axis, that is to say, the portionof projected light that becomes a shadow, is smaller. In addition, theportion of the heat channeling part 41 b at the reflector 11 issuing tothe outside is sealed with a cement 42 as, for example, shown in FIG. 3.FIG. 3 shows an example in which the width of the heat channeling part41 b was made narrower than the width of the heat absorbing part 41 a,but it is also possible that the width be made the same as that of theheat absorbing part 41 a and so forth.

[0081] In a heat releasing part 41 c, a cooling device 43, such as heatreleasing fins, is provided. It is to be noted that as the coolingdevice 43, in place of heat releasing fins, it is also possible to use acooling fan, a cooling module utilizing a Peltier element, a watercooling device, or the like. It addition, it is possible to use a steelcase having a high thermal conductivity for the cooling device 43.Furthermore, for the cooling device 43, these devices can be used incombination. Moreover, it is possible to circulate air in the spaceenclosed by the reflector 11 and the glass plate 12 between a radiator,disposed outside of the reflector, so that the inside of the lamp deviceis cooled.

[0082] According to the above-described construction, heat transmittedto the sealed portion 23 by thermal conduction and the like from thelight-emitting portion of the discharge lamp 21 is conducted to the heatreleasing part 41 c, outside of the reflector 11, by means of conductionfrom the heat absorbing part 41 a to the heat channeling part 41 b, andis released. For this reason, it is possible to maintain a lowtemperature at the sealed portion 23 and to prevent disconnection byoxidation, corrosion, and the like of the weld 29 a of the metal rod 29and the metal foil 27. In addition, when the heat absorbing part 41 a isprovided, at least near the front end of the sealed portion 23, it isall the more possible to improve the advantageous effects of preventionof disconnection by oxidation, corrosion, and the like of the weld 31 aof the metal rod 29 and the lead wire 31.

[0083] It is to be noted that the material used for the heat releasingdevice 41 is not limited to copper plate which was used above; as longas the material has a comparatively high thermal conductivity, the samecooling effects can be obtained.

[0084] In addition, in the heat channeling part 41 b and the like, aheat pipe, a thin pipe which forces the circulation of a coolant, or thelike may be used. In this case, the above-mentioned heat pipe or thinpipe may be affixed to the lead wire 31 and issued to the exterior ofthe reflector 11, and particularly, by coaxially aligning the heat pipeor thin tube with the lead wire 31, the amount of projected lightblocked by the heat pipe or thin tube and the lead wire 31 can be easilylimited to a small amount.

[0085] Furthermore, the heat channeling part 41 b may be provided, notonly in one location, but, as for example shown in FIG. 6, in aplurality of locations such that the amount of heat released is evengreater.

[0086] Moreover, in FIG. 3 an example is shown in which the lengths ofthe sealed portion 23 and the sealed portion 24 are made to be equal,but this is not the only possibility; the length of the sealed portion23 may be made longer as was the case in Example 1, or when the heatreleasing effects are sufficiently obtained by the heat releasing device41, the length of the sealed portion 23 may be made shorter.

EXAMPLE 3

[0087] An example of a lamp device constructed such that a dischargelamp is integrally formed with a glass plate and the front end of asealed portion contacts outside air.

[0088] As shown in FIG. 7, in a discharge lamp 21, the front end of asealed portion 23 is integrally formed with a glass plate 12 and a weld31 a of the front end of a metal rod 29 and a lead wire 31 is exposed tothe side of the exterior surface of the glass plate 12. In addition,near the glass plate 12, a cooling fan 51, blowing outside air on theexterior surface of the glass plate 12, is provided.

[0089] By constructing a lamp device as described above, because heatfrom the front end of the sealed portion 23 is released from theexterior surface of the glass plate 12 and the like, the temperaturenear a weld 29 a of a metal foil 27 and the metal rod 29 is restrictedto a low temperature, and disconnection, due to oxidation, corrosion,and the like of the weld 29 a and so forth, is prevented.

[0090] It is to be noted that, in place of the cooling fan 51, heatreleasing fins, a cooling module utilizing a Peltier element, or thelike may be provided near the periphery of the glass plate 12 such thatprojected light is not blocked, or these devices may be combined and soforth. Furthermore, when, by natural convection near the exteriorsurface of the glass plate 12 and the like, the temperature near theweld 29 a is sufficiently restricted to a low temperature, it is notnecessary to provide the cooling fan 51 or the like.

[0091] In addition, in the example of FIG. 7, the front end of thesealed portion 23 only protrudes slightly from the surface of the glassplate 12, but when it is possible that the whole length (length in thedirection of the optical axis) of a lamp device 10 be long, as shown inFIG. 8, the front end of the sealed portion 23 may further protrude fromthe surface of the glass plate 12. In this way, by positioning the weld29 a almost beyond the surface of the glass plate 12, the temperaturenear the weld 29 a can be easily restricted to an even lowertemperature.

[0092] Furthermore, in the example in FIG. 7, the length of the sealedportion 23 is made longer than that of the sealed portion 24 as inExample 1, but there are other possibilities. Namely, when the distancebetween the light-emitting portion of the discharge lamp 21 and the weld29 a is short, because the temperature near the weld 29 a is restrictedto a low temperature due to the release of heat from the surface of theglass plate 12, the sealed portion 23 may be made the same length as thesealed portion 24 as shown in FIG. 9 or shorter than the sealed portion24. For this reason, a lamp device 10, utilizing a discharge lamp 21having a comparatively large size in comparison to the size of thereflector 11, can be easily constructed.

[0093] Moreover, in addition to a construction as described above, inwhich a discharge lamp is integrally formed with a glass plate, it isalso possible to provide a heat releasing device 41 as shown in Example3.

EXAMPLE 4

[0094] An additional example of a lamp device, like that of Example 3,constructed such that a discharge lamp is integrally formed with a glassplate and the front end of a sealed portion contacts outside air isexplained.

[0095] As shown in FIG. 10, a hole 12 a is provided in the centralportion of a glass plate 12 such that an end of a sealed portion 23passes through the hole 12 a. The gap between the sealed portion 23 andthe hole 12 a is bonded and sealed by, for example, a filler 52 composedof substances different than those of the glass plate 12 and the sealedportion 23. It is preferable that the filler, more specifically, becomposed of a transparent material such as glass having a lower meltingpoint than the glass plate 12 or the sealed portion 23.

[0096] In this way, after separately forming the glass plate 12 and thesealed portion 23, by joining both members, the production process,compared with that of a lamp device of Example 3, utilizing an arc tube21 integrally formed with a glass plate 12, is simplified.

[0097] Even when constructed as described above, as in Example 3,because heat from the front end of the sealed portion 23 is releasedfrom the exterior surface of the glass plate 12 and the like, indeed thetemperature near the weld 29 a of the metal foil 27 and the metal rod 29is restricted to a low temperature, and disconnection, due to oxidation,corrosion, and the like of the weld 29 a and the like, is prevented.

[0098] In the present Example also, it is possible to apply the manyvariations that were explained in Example 3.

[0099] It is to be noted that in each of the above-described Examples,examples utilizing an ellipsoidal mirror as the reflector weredemonstrated, however the reflector is not limited to an ellipsoidalmirror, and it is also possible to utilize a concave mirror such as aparabolic mirror.

[0100] It is also to be noted that, in the above-described Examples,examples, all of which utilized a discharge lamp having an operatingpressure of approximately 200 atmospheres, were explained, but thepresent invention may be applied to a lamp device utilizing a dischargelamp operated at a lower pressure, for example, a pressure of 100atmospheres or lower.

[0101] In addition, the present invention is not limited to lamp devicesutilizing discharge lamps having the foil sealed construction asexplained in the Examples, but may be suitably applied to lamp devicesutilizing all kinds of discharge lamps having welded parts of wiringmembers near the discharge lamp at which there is a risk of thermaldegradation due to high temperatures Furthermore, the gas inside thelamp device is not particularly specified, but it is possible to encloseair or an inert gas such as argon gas.

[0102] Moreover, in addition to each of the above-describedconstructions or in place of each of the above-described constructions,gas inside the lamp device may be circulated between a radiator on theoutside such that the inside of the lamp device is cooled.

INDUSTRIAL APPLICABILITY

[0103] According to the present invention, because the temperature ofthe front end of a sealed portion can be restricted to a low temperatureand disconnection due to oxidation and the like of the welds of wiringmembers and the like can be prevented, a lengthening of lamp life and adecline in the percentage of defective lamps can be expected.Furthermore, increase in lamp power and reduction in the size of thereflector can be achieved without difficulty.

[0104] In addition, according to the present invention, because anexcessive temperature rise inside the lamp device can be prevented evenif the lamp device is hermetically sealed, it is possible to limitexplosive sounds from the arc tube and to ensure prevention of thescattering of glass fragments and the dispersal of mercury vapor.

What is claimed is:
 1. A lamp device comprising: a discharge lampcomprising an arc tube, the arc tube enclosing luminescent materials andhaving disposed therein a pair of opposing electrodes, and a pair ofsealed portions extending from the arc tube; a reflector which reflectslight radiated by the discharge lamp; a transparent member covering anopen end of the reflector and accommodating the discharge lamp in aspace between the transparent member and the reflector; and means forpreventing an excessive temperature rise wherein the temperature rise ofwelded parts of wiring members electrically connected to the electrodesis restricted.
 2. A lamp device according to claim 1, wherein the sealedportions have a foil sealed construction.
 3. A lamp device according toclaim 1, wherein an inside space of the reflector and the transparentmember is hermetically sealed in a gastight manner.
 4. A lamp deviceaccording to claim 1, wherein the pair of sealed portions have differinglengths and the means for preventing an excessive temperature rise issuch that the longer sealed portion is on the side of the transparentmember and the shorter sealed portion is on the side of the base of thereflector.
 5. A lamp device according to claim 4, wherein an end of thesealed portion on the side of the transparent member is positioned nearthe transparent member.
 6. A lamp device according to claim 1, whereinthe means for preventing an excessive temperature rise is means forchanneling heat such that heat from the sealed portion disposed on theside of the transparent member is conducted to the exterior of the lampdevice.
 7. A lamp device according to claim 1, wherein the means forpreventing an excessive temperature rise is such that the sealed portiondisposed on the side of the transparent member is integral with thetransparent member.
 8. A lamp device according to claim 1, wherein themeans for preventing an excessive temperature rise is such that thefront end of the sealed portion disposed on the side of the transparentmember projects into the exterior of the transparent member.
 9. A lampdevice according to claims 6, 7, or 8, further comprising cooling meansfor removing conducted heat to the exterior of the lamp device.
 10. Adischarge lamp comprising: an arc tube enclosing luminescent materialsand having disposed therein a pair of opposing electrodes; and a pair ofsealed portions extending from the arc tube, the pair of sealed portionshaving differing lengths.